Transportation costs associated with an aqueous diluent portion of a formulated aqueous product can be a significant part of the cost of aqueous liquid products. Products, such as sanitizing or cleaning solutions, when used in large amounts can be expensive to use due to transportation costs associated with the aqueous portion. For this reason, many commodity liquid products are shipped from the manufacturer as an aqueous concentrate, an aqueous alcoholic concentrate, or as a viscous concentrate to be diluted in a dispenser with an aqueous diluent at the use locus or site. For example, liquid detergents and cleaning solutions used in hospitality locations, institutional or industrial installations such as hotels, hospitals, restaurants, and the like are often shipped as liquid concentrates that are mixed and diluted using a dispensing device at an appropriate ratio to obtain a useful solution.
Concentrates can be diluted in many ways, varying from manually measuring and mixing to utilizing a computer-controlled dilution device. One common dilution technique involves utilizing a dispensing device that combines, under mixing conditions, a flow of concentrate and a flow of diluent. The flow of the liquid diluent can be directed through an aspirator such that, as the diluent passes through the aspirator, a negative pressure arises inside the aspirator drawing the liquid concentrate into the aspirator to mix with the liquid diluent. Both U.S. Pat. No. 5,033,649 to Copeland, et al. and U.S. Pat. No. 4,817,825 to Freese disclose dispensers having aspirators for diluting liquid concentrates to produce liquid products in this general way. Such aspirator-type dispensers have been used for diluting a liquid concentrate of an arbitrary viscosity with a low viscosity liquid diluent to produce a use solution of intermediate or low viscosity, i.e., the viscosity of the product falls between the viscosity of the concentrate and the diluent.
A use solution of high viscosity is often desirable. Increased viscosity can increase clinging ability to surfaces of an inclined or vertical substrate for more effective and prolonged contact. In addition, a high viscosity hand soap is often easier to use and tends to feel better than low viscosity hand soaps. Relatively viscous use solution made by diluting a low viscosity liquid concentrate with water to form a high viscosity dilute product are described in the prior art. For example, see European Publication No. 0 314 232; U.S. Pat. Nos. 5,057,246 to Bertho et al.; U.S. Pat. No. 5,922,667 to van Baggem et al.; and U.S. Pat. No. 5,922,664 to Lao et al.
A dispenser for dispensing a viscous use solution by diluting a less viscous concentrate is described in U.S. Pat. No. 5,816,446 to Steindorf, et al. which is assigned to Ecolab Inc. of Saint Paul, Minn., the assignee of this application.